Venting primary battery



March 24, 1953 2,632,784

P. A. MARSAL ET AL VENTING PRIMARY BATTERY Filed March 29, 1950 INVENTOPAUL A. MA SSAL 4 RUSSELL P. FOX

' BY WW I A ORNEY Patented Mar. 24, 1953 VENTING PRIMARY BATTERY Paul A.Marsal, Rocky River, and Russell P. Fox, Cleveland, Ohio, assignors toUnion Carbide and Carbon Corporation, a corporation of New YorkApplication March 29, 1950, Serial No. 152,584

2 Claims. (01. 136-133) This invention relates to primary galvanicbatteriescf the dry type and refers more particularly to batteriescomposed of a plurality of flat cells and to improvements in ventingsuch batteries.

One of the problems which has given battery makers continued difficultyis that of sealing a dry primary cell or battery of cells againstleakage of liquid released by the interaction of the chemical componentsof the cell or battery upon discharge while at the same time providingfor the release of internally generated gas. The problem is aggravatedin multi-cell batteries and has proved particularly difiicult ofsolution in batteries comprising a plurality of vertically stacked flatcells.

The principal object of thepresent invention is the provision ofimproved means for sealing a battery of fiat cells againstleakage ofliquid and also providing improved venting of gas from such battery.

In the accompanying drawing:

Fig. 1 is a diagrammatic view in perspective of a battery of cells to besealed in accordance with the invention;

Fig. 2 is an elevational view of a battery embodying the invention, partbeing broken away;

Fig. 3 is a horizontal sectional view of a battery embodying theinvention, part being broken away; and 1 Fig. 4 is a partial view inenlarged detail of an adhesive-coated tape used in one embodiment of theinvention.

The invention comprises a battery of flat galvanic cells stacked inconventional fashion and provided with a plurality of gas-permeablefibers extending along a side of the stack of cells and communicatingwith the ambient atmosphere, and a plastic-coated wrapper sealed to thestack of cells and enclosing the gas-permeable fibers. The fiberspreferably are in tape form; the tape may be of open mesh material suchas cheesecloth or tobacco cloth or may be closely woven.

Referring to the drawing, a battery embodying the invention may beformed from a stack S assembled in conventional manner from a pluralityof individual cells 10. Each of the cells I is provided with itsindividual wrapper or container l I of thermoplastic materialconstructed and arranged in conventional manner to provide seriescontact between the cells I0. Each of the individual cells is identicalsave for the end cells v l 2, l3, which are provided with suitableterminals l4, I5. Along at least one side of the stack S is provided atape 16 composed of gas-permeable fibers. The tape lfiis folded over theend cells 2,173 toward the center of the stack S so that the ends of thetape [6 communicate with the ambient atmosphere. A wrapper W, preferablyhaving at least two layers ll, l8, at least the inner layer ll beingcomposed of electrolyteproof material and preferably of thermoplasticmaterial compatible with the containers or wrappers ll of the individualcells [0 encloses the stack S and is sealed to the sides of itsindividual cells. As an additional precaution against leakage, a waxlayer l9 (Fig. 3) may be formed about the wrapped battery, for exampleby dipping the battery in molten wax, and a conventional label 20 thenapplied.

To assemble a battery embodying the invention, the individual cells It!and the terminal cells l2, I3 are made and stacked in conventionalmanner. The tape I6 is then placed in position and'may be heldtemporarily by an adhesive. While the stack of cells is maintained underendwise pressure, the wrapper W is applied and caused to adhere to it,preferably by heat-sealing. The wrapper W must not cover the ends of thelongitudinal fibers of the tape [6. A convenient procedure is to applyheat both to the stack of cells and to the Wrapper sufficient to causethe thermoplastic containers or wrappers of the individual cells and.the thermoplastic layer I! of the wrapper W to soften sufficiently tounite under the applied pressure, care being taken of course not to heatthe cells of the battery to a temperature high enough to damage them.The outer layer l8 of the wrapper W may serve as the label for thebattery or as indicated above the battery may be coated with wax and aseparate label applied.

As above stated, the gas-permeable fibers utilized in the invention aremost conveniently applied in the form of a tape which may be of openmesh or may be closely woven. A closelywoven tape is advantageous inprovidin more fibers. When an open mesh tape is used, the softenedplastic I! of the wrapper W is forced into the interstices of the openmesh tape and is bonded to the individual containers ll of the cells l0,thus effectively barring any path for escape of liquid. When aclosely-woven tape is used, however, it is diflicult to force theplastic ll of the wrapper W through its interstices. In such casetherefore, it is desirable to provide a thin, gas-permeable coating ofthermoplastic adhesive 2| (Fig. 4) on the side of the tape 16 that is tobe sealed to the container I l of the cells I0.

This adhesive then serves to block the passage of liquid.

Many batteries have been assembled embodying the invention. Suchbatteries have proved to be substantially free of leakage under allordinary conditions and have exhibited little or none of the bulgingcharacteristic of insufliciently vented batteries. Any gas internallygenerated apparently escapes from the individual cells through theinterstices between the cells and then is transmitted through thegas-permeable fibers to the ambient atmosphere thereby preventing theincrease of pressure within th battery. The electrolyte-proof innersurface of the wrapper prevents escape of liquid.

Based on the tests just mentioned a preferred construction is one inwhich the containers of the individual cells are composed of a copolymerof vinyl chloride and vinyl acetate, a closelywoven, plastic-coatedlinen tape is used, and the wrapper is paper which has been coated onone surface (to be the inner surface) with vinyl chloride-vinyl acetatecopolymer. In this construction the plastic coating on the wrapper maybe 0.003 to 0.006 inch thick.

The fibers utilized in the battery of the invention may be of vegetableor animal origin or may be synthetic, but in any event must begaspermeable.

We claim:

1. A battery of rimary galvanic cells comprising a stack of fiat cellsassembled under endwise pressure eachprovided with an individualthermoplastic container, said cells being electrically inter-connectedin series; a, gas-permeable fibrous tape extending along at least oneside of said stack but outside of said cells and communicating with theambient atmosphere only at at least one end or said stack; and anelectrolyte-proof 4 wrapper for said stack, said wrapper beingintegrally united to said stack and overlying said tape and serving tomaintain said stack in endwise compression.

2. A battery of primary galvanic cells comprisins a stack of flat cellsassembled under endwise pressure each provided with an individualthermoplastic container, said cells being electrically inter-connectedin series; a gas-permeable fibrous tape extending along at least oneside of said stack but outside of said cells and communicating with theambient atmosphere only at at least one end of said stack; and anelecrolyte-proof Wrapper for said stack, at least the inner surface ofsaid wrapper being composed of thermoplastic material compatible withthe said containers of the individual cells of said battery, and saidwrapper being integrally united to said stack and overlying said tapeand serving to maintain said stack in endwise compression.

PAUL A. MARSAL. RUSSELL P. FOX.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,487,494 Tyrrell Mar. 18, 19241,855,677 Huntley Apr. 26, 1932 1,969,630 Sprague et a1. Aug. 7, 19342,262,836 Deibel Nov. 18, 1941 2,272,969 French Feb. 10, 1942 2,307,764Deibel et a1 Jan. 12, 1943 FOREIGN PATENTS Number Country Date 482,363Great Britain Mar. 24, 1938

